1. Field of the Invention
The present invention relates to a mobile communication terminal such as a cellular phone, a personal digital assistant (PDA) or a personal computer (PC) and more particularly, to a mobile communication terminal that includes a built-in antenna.
2. Description of the Related Art
Recently, in a mobile communication terminal represented by a cellular phone, a PDA, or a PC, there has been added a variety of diversified functions such as a web access function or a remote control function relevant to a peripheral device, a function serving as a season ticket, and an electronic money settlement function as well as a telephone communication function or an electronic mail transmitting and receiving function. With respect to only a communication interface, in addition to a communication interface for mobile communication using a G (giga) Hz band, there has been introduced a terminal that includes plural types of communication interfaces in order to use Bluetooth (registered trademark), a wireless local area network (LAN) or the like. For this reason, there is a tendency that a mobile communication terminal becomes increasingly large in size. On the other hand, there is a user's demand for further reduction in size and weight in order to improve portability.
Therefore, a variety of downsizing techniques have been proposed. As one of such techniques, an antenna downsizing technique is exemplified. For example, there has been proposed a technique in which part of a casing is composed of an electrically conductive material, and a conductor section of this casing is connected to a radio communication circuit, thereby operating as part of an antenna (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-274730).
However, in the foregoing conventional technique, there is not disclosed in detail a technique for providing part of the casing made of an electrically conductive material or a technique for connecting a conductor section of the casing and a radio communication circuit to each other, making it difficult to carry out the invention. Therefore, there has been a keen desire for establishment of an antenna downsizing technique that can be carried out.